In devices adapted for transmitting and/or receiving information via a digital data communication bus-system, it can be advantageous to provide a low-power bus monitoring mode of operation, in which the device conservatively consumes power to monitor incoming data transmitted over the data bus to detect a signal or message intended to instruct the device to resume a normal mode of operation.
For example, it is known in the art for Control Area Networks (CAN), e.g. in accordance with the standard ISO11898-6, to provide a selective wake-up functionality. This may advantageously allow a reduction of power consumption in such network. For example, a node on a CAN bus system in a vehicle may not be needed a large fraction, e.g. 80%, or even higher, e.g. 90% or 95%, of the time. While a node without selective wake-up capabilities might consume, for example, a few watts of power, e.g. 2 W, when waiting for a request, a node or group of nodes can be maintained in the selective wake-up state without wasting power in a CAN network that supports partial networking, as known in the art. Thus, power consumption can be severely reduced during an idle mode of a node when the node does not need to be active.
Partial networking enables a node or group of nodes to be woken separately from other nodes connected to the bus system. A wake-up signal may be transmitted in the form of a predetermined CAN message, e.g. as opposed to a generic wake-up in response to any bus activity, such as defined by the standard ISO11898-5. However, the CAN transceiver device may thus be required to monitor and analyze a bit stream transmitted via the bus for specific wake-up messages under severe power limitations, e.g. since only limited power consumption is allowed during its inactive state. For this, the receiver needs to be able to properly sample the incoming data bit stream, while, for example, clock accuracy in this inactive mode can be limited due to the power requirements.
The U.S. Pat. No. 8,989,210 discloses a method for unambiguously waking users of a bus system. The method involves a multi-phase approach to decide if a bus node wakes from its inactive state based on a message transmission over the bus. In a first phase, an incoming message is detected. In a second phase, the correct communication protocol for the message is validated, and in a third phase, the bus node can be selected by processing logic information in the message.
The U.S. Pat. No. 7,430,261 discloses a method and a bit stream decoding unit that uses majority voting. It this method, a detection window is defined, and majority voting on consecutive samples is used to detect a bit value. This sampling approach is repeated to determine each bit of the transmitted data bit stream.